DE1421548C3 - Fuel element - Google Patents

Description

The invention relates to a fuel element with an aqueous adsorbed on an electrolyte carrier Electrolyte, which has two gas-permeable, hydrophobic electrodes and with which in particular can advantageously generate electricity. In a cycle, electricity is generated by Fuel gases and oxidizing gases are consumed and generated again by electrolysis.

Many of the fuel elements currently available have the disadvantage of being relatively proportionate have low efficiency per unit volume. It also excludes the use of free flowing and occasionally circulating electrolytes their application in a gravity-free environment off unless cumbersome additional control devices are made.

In Belgian patent specification 596 662 and British patent specification 894 530 a fuel element described, which consists of an ion exchange membrane made of a resin mass as an electrolyte, the electrodes are firmly attached to their two larger surfaces. Such a fuel cell possesses high efficiency per unit volume when used continuously as an electrical power source is operated. Such fuel elements are not affected by operation when the current is drawn continuously as the electrolyte consists of ionically active groups in the membrane itself i: nd ' these groups cannot be leached by the water caused by the reaction in the cell arises.

It has now been found that this increases the maximum possible capacity of such a fuel cell can be that the ion exchange membrane from the resin composition with an electrolyte, for. B. one Sulfuric acid solution, soaks so that the absorbed acid increases the conductivity of the membrane and the Increases the power of the electrodes of the cell. Unfortunately, the increase in performance is limited in time because the water, which has arisen as a result of the reaction in the cell, dilutes the unbound electrolyte and pulls it off when you leave the element, so that the effect is finally achieved with continued operation such an equilibrium is completely lost.

Such complete dilution would not occur if the element were in circulation would, in which the water formed during the current withdrawal of the element of the membrane and the Electrolyte is fed back in, so that the fuel and the oxidizing gases during the electrolysis be renewed in the element. In order to achieve this possibility, one must have a process invent, with the help of which the water formed is stored and in the electrolysis the element is fed back.

The invention was therefore based on the object of a novel fuel element for gaseous fuels to create that works in repetitive and regenerating cycles and has a high Efficiency per unit volume, a large capacity, a low polarization, a high resistance and has great chargeability.

The invention relates to a fuel element with an aqueous electrolyte solution which is adsorbed on an electrolyte carrier which is arranged between two gas-permeable, hydrophobic electrodes, which is characterized in that the electrodes contain gas-adsorbing metal particles with a surface area of 10 to 100 m ² / g, which are connected with polytetrafluoroethylene to form a uniform mass, with 0.214 to 2.14 parts by volume of metal falling on one part by volume of polytetrafluoroethylene.

As is generally the case, the volume is determined on the basis of the consistency of the material.

Various metals can be used for the electrodes of the fuel element according to the invention will. Suitable metals are, for example, the noble metals of Group VIII of the Periodic Table of the elements, d. H. Rhodium, ruthenium, palladium, osmium, iridium and platinum. More usable Metals of group VIII are: nickel, iron or cobalt as well as metals that are catalytic gases adsorb, ζ. B. silver, copper and metals of the transition series, e.g. B. manganese, vanadium or rhenium. In addition to electrodes made of these metals, electrodes made of stainless steel can also be used Steel, iron or nickel are made up and deposited on the platinum or palladium black would. Furthermore, electrodes made of metal oxides or carbon can be used with Platinum or palladium have been activated, or electrodes made of carbon that have been activated with iron oxides, magnesium, Cobalt or copper have been activated.

Since the adsorption of gases by solid bodies depends on their surface area, it is recommended that the electrodes have as large a surface as possible and that this is activated as strongly as possible in order to adsorb gases. It should also provide a "possible uniform coating on the critical surface of the electrolyte carrier of a maximum efficiency within the fuel element, each electrode to achieve. For these reasons, the use of finely divided metal powders, which provide a large surface area is recommended, at least 10m ² ie per gram and preferably at least 100 m ² per gram In order to achieve the greatest possible efficiency of the element, one should use electrodes made using the highly active metal powders of Group VIII, for example with platinum or palladium black or Raney nickel Groups VIII have the further advantage that their resistance to acid corrosion enables them to be used in conjunction with a cation exchange resin composition used as an electrolyte carrier, and corrosion is not as pronounced in fuel elements having an anion exchange membrane . In such a case, a long element life can be achieved by using metals that are alkali-resistant, e.g. B. Group VIII metals including nickel or cobalt and the other known gas adsorbing metals, e.g. B. rhenium. The choice of metals will depend on the intended use, the desired life and the gases used as fuel and oxidant.

During the manufacture of the electrodes, the finely divided metal powder is mixed with polytetrafluoroethylene, so that there is a uniform dispersion of the metal powder in the polytetrafluoroethylene.

Good results are obtained if an aqueous emulsion of polytetrafluoroethylene with 2 to 20 g of the metal powder per gram of polytetrafluoroethylene in the solution and as thin a film as possible

Pour onto a metal foil or plate and form the desired shape of the electrode. Subsequently the water is evaporated from the emulsion and the polytetrafluoroethylene under pressure sintered at a temperature high enough to cause sintering of the individual polytetrafluoroethylene particles to effect. The electrode is then removed from the infusion surface and placed in the desired area Format cut if this did not already exist at the time of casting. Through such a procedure will a gas-permeable, electronically conductive, water-repellent electrode with great mechanical strength delivered without further processing is required. On the other hand, the metal powder mixed with dry, powdered polytetrafluoroethylene, then shaped, pressed and sintered, so that either a thin film or a thick mass is formed which is formed into thin films or can be cut. These are used as electrodes. One such procedure however, it is more difficult and time consuming than the application of an emulsion.

It "can also be a fiber fabric or a mat, which preferably consists of fibers and which the withstand strongly acidic or basic conditions in the fuel cell and, for example, from Glass, asbestos, acrylonitrile, vinylidene chloride or polytetrafluoroethylene can exist with the mixture made of polytetrafluoroethylene and metal powder are soaked and coated.

In the fuel elements according to the invention, the electrolyte carrier normally consists of one Ion-exchange resin mass impregnated with an aqueous solution of the electrolyte. The electrolyte carrier can also consist of one in the context of the invention gel-like, powdered or fibrous material or a foam, if this material is so porous that the electrolyte is adsorbed in aqueous solution with the help of capillary forces can. If the electrolyte carrier consists of fibers, then these can be woven or non-woven Form a mat or a felt. A woven fabric is used to fill the gaps do not provide a sufficient gas barrier, then a layer of densely stored gas can act as a barrier Fibers that are similar to felt or that can be supplied by paper-making processes, incorporated into the electrolyte carrier and this layered electrolyte carrier can be used.

Another requirement of the electrolyte carrier is that it have sufficient mechanical strength must have to withstand the pressure differences in the cell. He must not be electronically conductive although ionic conductivity is desirable. But above all, the electrolyte carrier must be chemical be neutral to the effects of the electrolyte. Suitable substances are, for example: asbestos, vinylidene chloride, Acrylonitrile, polytetrafluoroethylene, which are woven, mat-like, felt-like or porous shaped, cast or calendered form can be used, or silica gel (for acidic electrolytes), porous ceramic materials, ion exchange resin membranes.

The fuel elements, which consist of such substances, can be used at room temperature and atmospheric Pressure operated. If desired, the elements can also be operated in a superatmospheric or subatmospheric environment must be between the freezing point and the boiling point of the electrolyte present. To one To avoid breakage of the electrolyte carrier should be the pressure of the fuel and the oxidizing gas when touching the membrane should preferably be the same, but under no circumstances should the resistance of the Exceed electrolyte carrier.

The ion exchange resin membranes are ideally suited for the production of solid Electrolyte carriers according to the invention, since they easily adsorb the electrolyte due to their structure and are chemically highly resistant to their effects. Besides, let them Process themselves into suitable carriers through a wide variety of manufacturing processes and are natural Gas barriers that prevent fuel and oxidizing gases from mixing. The electronic The conductivity of the membrane is negligible, the electrolytic conductivity can be increased, and the membranes do not let uncharged gases through. The membranes are self-supporting and can be reinforced so that they have great chemical resistance. You can also are made of thin films with a large surface, so that favorable dimensions for the Fuel cell and its operation result.

After the membrane has been prepared according to the usual method, the water of hydration replaced by an aqueous electrolyte by placing the membrane in the appropriate acidic or basic solution dips. Before the membrane is inserted into a fuel element, it can be dried off so that there is no free flowing liquid in the cell. The membrane can can then be viewed as a gel-like electrolyte carrier for the unbound electrolyte. The best results are with a strong acid in the case of a cation exchange resin and with an anion exchange resin achieved with a strong lye. The concentration of the electrolyte should be as high as be possible without affecting the chemical nature of the membrane and its mechanical and electrical Properties are adversely affected. On the other hand, the electrolyte should be chemically like this be that the electrolysis produces hydrogen and oxygen. The electrolyte must be in the aqueous phase be soluble and should have a sufficiently low vapor pressure that it does not turn into the gaseous Phase evaporates.

Because of the specified restrictions, the following electrolytes are recommended for cation exchange membranes made from a resin compound: sulfuric acid, phosphoric acid, the aromatic sulfonic acids, e.g. B. benzene mono-, di and trisulfonic acid, toluene mono-, di- and trisulfonic acid, naphthalenesulfonic acids z. For example, the mono-, -α- and -beta-naphthalenesulfonic acid, and u is the various naphthalene disulfonic acids. The like. M. Usually, acids and bases having a dissociation constant of at least 1 x 10 ~ ⁴ satisfactory, provided that an aqueous solution of the electrolyte can be electrolyzed so that hydrogen and oxygen are formed and that this is predominantly non-volatile. Examples of bases that can be used in connection with anion exchange resins are: sodium hydroxide, potassium hydroxide, lithium hydroxide, cesium hydroxide and rubidium hydroxide. Is the electrolyte carrier against both acids and against

Basically neutral, then the electrolyte can be either acidic or basic. Since inorganic acids, e.g. B. Sulfuric acid or phosphoric acid, and inorganic bases, e.g. B. sodium hydroxide or potassium hydroxide, are readily available commercially and are stable when operated in a fuel element, little are costly and highly ionizable in aqueous solutions, these are preferably used.

In the fuel element of the invention, hydrogen is preferred as the fuel gas and oxygen preferably used as an oxidizing gas.

When building the fuel element according to the invention, one electrode is placed on each of the two Main surfaces of the solid electrolyte carrier attached, the one with the desired aqueous solution of the electrolyte is soaked. Since the electrode has a somewhat limited electrical conductivity, the If the internal resistance of the element increases, it is advisable to connect the electrode with a current conductor to reinforce a material with good electrical conductivity.

This conductor can also be a part of the cell that reinforces the structure. Such Conductors can be suitably punched from a grid, metal wires, metal rods or or make expanded metal plates that do not prevent the fuel gas from contacting the electrode and which are electrically connected to the required line. Such conductors can either only be in contact with or embedded in the surface of the electrode, so that they form a unit with this. With only superficial contact of a conductor with gaps With the electrode, such a grid can have an electrode surface from a second Have membrane which is in contact with the opposite face of the conductor, so that a battery is formed when several elements are connected together. With such an arrangement the two electrodes that are in contact with the same conductor are the same electrical charge, since they come into contact with the same gas, d. H. either with the fuel or the oxidizing gas. In such an arrangement, the elements are connected in parallel.

Ribbed sheets or corrugated sheets, which are impermeable to gas, can also be used as current conductors. This ensures that the gas on one side of the grid is only one side of the electrode can touch. Such a conductor can serve as a partition between the two electrodes, see above that the fuel and the oxidizing gas come into separate contact with the same conductor, but with different electrodes. Such an arrangement of neighboring cells is called a series connection.

In general, the electrodes are made by having a slurry from the the desired weight fraction of the granular metal produces, so that an aqueous dispersion with 60 percent by weight solid polytetrafluoroethylene, which can be diluted with water if desired so that a texture is obtained which is easily applied to the desired surface can. Mix on an aluminum foil on which the outline of the desired electrode shape is marked has been. If a uniform suspension has been produced, then this is evenly distributed applied to the desired area and the water contained therein removed by drying in the air. The aluminum foil is then gradually placed on a hot plate within a few minutes heated so that the remaining water evaporates. The dried film adheres well to the aluminum foil and is easy to shape and edit. A second aluminum foil is dried over the Film is placed, and the resulting stratification is placed in a hydraulic press in which the electrodes

ίο at the temperatures given in the examples and pressing. After removal from the press, the electrodes are quenched in water and the aluminum foil in an aqueous solution of sodium hydroxide at a concentration dissolved from 10 to 20 percent by weight. The electrodes are strengthened so that they can be handled easily without damaging them. They are then rinsed off and stored in distilled water until used.

Preferred embodiments of the fuel element according to the invention are described in the following examples. Different electrolyte carriers, electrolytes and different concentrations of the metal particles are used on the electrode surfaces. The platinum catalyst of Examples 1 to 6 had a determined surface area of 10 m ² / g, and the palladium catalyst used in Example 7 had the same physical under-

partunaserad. _. ...

example 1

To determine the effect of the temperature and time used in manufacture, a series of electrodes were made from 17 mg platinum black and 1.6 mg polytetrafluoroethylene per square centimeter of the electrode. When pressing the electrodes, a pressing pressure of 75 kg / cm ^{2 was} applied, which was maintained for 2 and 10 minutes at a temperature of 330 to 390 ° C.

These electrodes were used as an oxygen electrode in the fuel element, and the hydrogen electrode was made of the same composition but was pressed ^{at a pressing pressure of 469 kg / cm 2.} The polarization of the elements was determined when drawing electricity and producing electricity using an electrolyte carrier made of an ion exchange resin having the hydroxyl group as a mobile ion. The equilibrium was established by an aqueous solution of 5.4 mol of potassium hydroxide. To make it easier to compare the various elements, the polarization information for each element was entered in a rectangular coordinate system and the potentials of the elements were read from the smooth curves with rounded values of the current strengths. The information has been compiled in Table I.

Table I.

Current density sow
33O ° C erstoffelcktroden.
Temperature unc
350 ° C at the specified
Time made
370 ⁰ C 2 10 0.93 2 10 0.93 nen
3 93'C Minutes Tension in
with electricity the element
withdrawal mA / cmr 2 0.97 0.93 2 5 0.95 0.93

continuation Temperature and time established 370 ° C Minutes 2 10 2 10 0.90 0.90 0.90 1.54 1.55 1.56 39O ⁰ C Tension in the element 0.87 0.87 0.86 1.58 1.58 1.61 35O ⁰ C when drawing current 0.81 0.80 0.79 1.62 1.64 1.65 2 Current density 0.92 0.75 0.74 0.74 1.70 1.74 1.74 Oxygen electrodes. at the specified 0.88 Tension in the element 1.78 1.83 1.82 0.81 in electrolysis 0.90 mA / 'cm ^! 0.76 1.54 0.86 330 C 1.59 0.80 1.64 0.74 10 2 1.74 20th 1.83 40 1.53 60 0.92 1.56 0.88 1.61 0.82 1.68 5 " 0.77 1.75 10 20 ■ 40 1.54 60 1.56 1.61 1.69 1.77

Weight ratio Sp 1.53 26: 2.4 26: 5.9 1.58 26:12 1.62 Current density 1.58 annung in the eggs 1.63 snt 1.72 . mA / cm ² from platinum to polytetrafluoroethylene 1.63 in electrolysis 1.72 1.87 5 y . 26: 1.2 1.71 1.56 1.89 1.78 1.59 - 5 1.65 ¹⁰ 1.74 20th 1.82 40 60

The data indicate that the temperature and time of manufacture can be varied widely without affecting the performance of the element. However, it was observed that electrodes, which had been pressed at a temperature of 33O ⁰ C, were mechanically rather weak compared to the other electrodes. A temperature of 330 ° C should therefore be the minimum temperature that is used when pressing and sintering the electrodes. The temperatures during production should preferably be between 350 and 390 ° C., with a time of 2 minutes being sufficient.

Example 2

In order to determine the effect of the ratio of catalyst to polytetrafluoroethylene, a number of electrodes were made from 26 mg of platinum black per square centimeter of the electrode and the proportion of polytetrafluoroethylene was selected differently. These electrodes were pressed for 2 minutes at 350 ° C. under a pressing pressure of 75 kg / cm ^2.

The performance of such electrodes was compared in the manner given in Example 1. The results are shown in Table II, with the current density versus the Voltage was applied.

Table II

The information clearly shows that when used

of 26 mg platinum per square centimeter of the electrode is a definite advantage if you do that Selects the ratio of platinum to polytetrafluoroethylene as high as possible and preferably at least about 2 parts by weight of platinum per part of polytetrafluoroethylene are used. The upper limit of this ratio is indicated by the mechanical inadequacy of those electrodes in which about 50 parts by weight Platinum per part of polytetrafluoroethylene are present. Such electrodes are so weak that such a relationship is meaningless. A ratio of 10 to 25 parts by weight of platinum per part of polytetrafluoroethylene gives the best results when making electrodes in the form of a thin film.

Example 3

In order to determine the effect of the amount of platinum used on the performance of a fuel element for a given size of the electrode, a series of electrodes were prepared using different amounts, the ratio of platinum to polytetrafluoroethylene in each case being 1: 0.09 mg. Electrodes of different thicknesses were made in this way, but they had the same platinum concentration per unit volume. The electrodes were molded for 2 minutes at 350 ⁰ C under a pressure of 75 kg / cm ^2. The performance of such electrodes in a fuel element was compared as described in Example 1 and the results are compiled in Table III, again with the current density plotted against the voltage.

Weight ratio Sp 0.97 26: 2.4 26: 5.9 0.93 26:12 0.90 Current density 0.93 admission in the eggs 0.87 ; nt 0.85 mA / cm ² from platinum to polytetrafluoroethylene 0.90 when drawing current 0.80 0.76 26: 1.2 0.83 0.97 0.70 0.61 0.78 0.93 0.62 5 0.89 10 0.81 20th 0.76 40 60

Table III

ever Concentration of the platinum 8.8 mg / cm ² 18 mg / cm ² 26 mg / cm ² 0.97 1.54 0.97 Current density Tension in the element 0.92 1.59 0.93 mA / cm ² Square centimeters of the electrode when drawing current 0.88 0.89 4.4 mg / cm ² 0.81 0.81 0.76 0.76 5 10 0.90 20th 0.88 1.56 40 0.84 0.94 1.59 60 0.78 0.91 * 0.73 0.87 Tension in the element 0.81 in electrolysis 5 0.77 10 1.56 1.60 1.55 1.58

409 631/245

Continuation rate

Current density Concentration of the platinum
per square centimeter of the electrode 8.8 mg'cm ' 18 mg'crrr 26 mg'cm ' 1.63 1.64 1.65 mA / cmr 4.4 mg'crrr Tension in the element
in electrolysis 1.72 1.74 1.74 1.65 1.80 1.83 1.82 20th 1.75 40 1.86 60

The data show that the amount of catalyst used per square centimeter of the electrode in the mentioned area has only a minor effect. However, the performance of the element decreases with the the smallest amount applied, as well as the strength, as the film formed compared to the other is very thin. So there is economic considerations and performance there is no reason to manufacture E-electrodes with a large cross-section other than mechanical strength, because the only effect in a prolonged way for the diffusion of the fuel and of the oxidizing gas would be.

Example 4

The effect of the use of different electrolyte carriers on the performance of the cell To determine, fuel elements were manufactured in which the electrolyte from an aqueous solution consisted of 5.4 moles of potassium hydroxide, with which a polyethylene terephthalate - polyester spun impregnated was, or an aqueous solution of 5.4 mol of potassium hydroxide, with which an asbestos spun or a cation exchange resin in which the mobile ion was the hydrogen ion, the Equilibrium was established by a 2normal aqueous sulfuric acid solution. In each of the cells the electrodes used contained 17 mg platinum black and 1.6 mg polytetrafluoroethylene per square centimeter the electrode. The electrodes were pressed for 2 minutes at 350 ° C and a pressure of 469 atm. When using the asbestos web as a carrier the electrodes were directly connected to the two main surfaces of the asbestos cloth during their manufacture been connected. The performances of the elements were compared with one another as in Example 1. The results are shown in Table IV below.

Table IV

Current density
mA / cm '

10 20th

Electrolyte carriers

made of polyethylene

terephthalate

Polyester-

Web

Asbestos

Cation exchange carriers

Voltage in the element when current is drawn

Current density
mA / cm ²

Electrolyte carrier

made of polyethylene

terephthalate

Polyester-

Web

Asbestos carrier

Cation exchange fluid

Voltage in the element when current is drawn

0.73 1.56 > ρ i e 0.76 0.79 1.63 0.67 1.60 0.70 0.73 1.69 1.67 η the element 1.77 1.79 electrolysis 1.87 Voltage i - 1.56 1.95 in the at 1.60 1.66 1.76 1.83 1 5

0.9!

0.87
0.81

0.94 0.89 0.84

0.93 0.90 0.85 40
60

10
20th
40
60

To improve the performance of the electrodes and the electrolyte in repeated cycles of electrolysis and to determine current consumption without having to calculate quantities that are completely in one closed system

produced three elements that had different electrolyte carriers. Element A consisted of the Carrier made of asbestos, in the element B made of an anion exchange resin and in the element made of, a cation exchange resin. The first two carriers were washed with an aqueous solution of 5.4 moles of potassium hydroxide and the third carrier soaked with 2N sulfuric acid. In all three elements the electrodes contained 17 mg platinum and 1.6 mg polytetrafluoroethylene per square centimeter of the electrode and molded under the conditions of Examples 1 and 2. The fuel elements were operated in cycles of 6 hours with 4.78 hours of electrolysis and 1.22 hours of current draw. During the current draw, the elements were controlled by pressure regulators with oxygen and Hydrogen was fed from storage tanks, and the air ducts of the elements were made by immersion the drainage pipes under the water surface are sealed by water. During the current draw the gas supply was regulated so that no gas could escape through the air ducts. During the Electrolysis increased the pressure in the element by a few centimeters of the water level, and the in Gases generated in the element were discharged from the element through the air ducts, but also would have can be collected and used again on the next discharge.

The current density during electrolysis and current consumption was adjusted so that the amount of electricity in the circuits was balanced, ie 13 mA / cm ² for current consumption and 3.3 mA / cm ² for electrolysis.

The invariability of the performance of such elements is demonstrated by the indications in Table V shown in which the specified voltages are the voltages at the end of electricity generation or Current consumption according to the specified circuits.

Table V Continuous Service Performance

Element A with asbestos backing electrolysis in the end of Element B with anion exchange carrier electrolysis Current draw Element C with cation exchange carrier electrolysis in the end of Days with a voltage i 1.72 Current draw Days with a tension at the end of 1.63 0.85 Days of tension 1.72 Current draw Cycle 1.74 0.80 Cycle 1.72 0.83 Cycle 1.74 0.80 0 1.77 0.74 0 1.74 ■ 0.82 0 1.73 0.77 1 1.79 0.72 1 1.77 0.80 1 1.74 0.75 2 1.91 0.79 ■ 2 1.79 0.78 2 1.74 0.76 4th 1.89 0.76 4th 1.80 0.77 3 1.74 0.75 8th 1.92 0.80 9 1.81 0.77 8th 1.74 0.74 15th 1.91 0.80 13th 1.80 0.78 10 1.75 0.74 21 - 1.91 0.78 17th 1.82 0.79 12th 1.75 0.74 28 0.78 24 1.80 16 1.76 0.74 39. 29 23 1.78 0.74 35 28 0.71 34

Example 6

Fuel elements with an alkaline electrolyte with which an anion exchange resin is impregnated (which was present as a membrane between electrodes with a diameter of 10.2 cm), were operated in repeated cycles for a long time. These elements were hermetic sealed so that they could be operated in a completely closed circuit. The housing the elements consisted of circular plates made of stainless steel with gas storage chambers in their end faces were incorporated. Ribs in the pantries served as reinforcement for the Electrodes and as pole grids. The hydrogen chamber was twice the volume of the oxygen chamber. Cord rings on both sides of the membrane were used to seal. A third ring was for the circumference of the membrane was required to prevent the water from entering the atmosphere evaporates.

Different pressures occur when the element is in operation when the ratio of the hydrogen and oxygen chamber is not exactly 2: 1, and this puts stress on the electrodes and the electrolyte carrier between the two chambers.

Conventional manufacturing methods find it difficult to provide such accuracy. A pressure equalization was created by connecting the chambers to a pressure equalization device that consists of a flexible rubber membrane between the hydrogen and oxygen chambers. A Yielding of the membrane adjusted the volume ratio so that pressure equalization took place.

The electrodes in the element of this example were manufactured using the methods already described, only the previous electrodes were smaller. In this case they contained 23 mg platinum black and 3.1 mg polytetrafluoroethylene per square centimeter of the electrode. The hardening temperature was 357 ° C. and pressing was carried out for 2.5 minutes with a pressing pressure of 136 kg / cm ² . The electrolyte carrier was an anion exchange membrane that had been soaked with 30% potassium hydroxide.

The prescribed cycle is described by the information in Table VI. The operation was carried out with the cell sealed from the atmosphere. During the first 413 cycles was electrolyzed for 55 minutes, during which time the gas pressure in both the Hydrogen and oxygen chambers to about 4.4 atm. The cell was turned on for 40 minutes removed before electrolyzing again. In those 40 minutes she was completely discharged.

After 413 cycles, the operation was slightly modified. A pressure regulator was on the element attached, and the electrolytic current and operating pressure were increased. The pressure regulator was adjusted so that the electrolysis current is interrupted when a gas pressure of 7.8 atm in the chambers had been achieved. That happened after less than 55 minutes allotted for electrolysis, and the element was only switched to power consumption after the full 55 minutes had elapsed. The current draw duration was 35 minutes. In Table VI

information about the performance is compiled.
Table VI

number of electrolysis entire
Amp. volt
through
cut Current draw entire
Amp. volt
through
cut Cycles
90 minutes each mA / cm ² 0.88 1.72 mA / cm ² 1.32 0.65 44 10.9 0.88 1.65 16.3 1.30 0.69 100 10.9 0.88 1.77 16.0 1.21 0.64 195 10.9 0.88 1.65 14.9 1.20 0.62 303 10.9 0.86 1.70 14.8 1.26 0.70 413 10.9 1.10 1.70 15.5 1.28 0.64 502 13.6 1.10 1.72 15.8 1.28 0.65 612 13; 6 1.10 1.73 15.8 1.30 0.66 725 13.6 1.10 1.71 16.0 1.20 0.61 838 13.6 1.10 1.80 1-4.8 1.24 0.64 886 13.6 1.10 1.72 15.3 1.25 0.64 950 13.6 1.10 1.75 15.4 1.24 0.64 993 13.6 15.3

Example 7

Fuel elements made and tested as in Example 6 were made using Made palladium black instead of platinum black. Were such fuel elements the Subjected to the same operating conditions as in Example 6, it was then found that the use of Instead of platinum, palladium had no appreciable effect on the operation of the element.

When the electrolyte carrier for the examples was made from a polyester fabric, six Tried strengths to find the right one for the amount of electrolyte required. Besides that a layer of filter paper was placed in the center of the assembly, creating a reliable gas barrier was present. When using asbestos a layer with a thickness of approximately 0.2 cm is used and the electrodes are firmly attached to the surface of the asbestos fabric, the Asbestos foil the one layer of an aluminum foil when pressing and forming the two electrodes replace.

The processes described are not restricted to the use of a platinum catalyst, but rather can be used when using other metal catalysts such. B. the already mentioned catalytically effective metals, such as silver, palladium, activated carbon, with a coating of such metals perform as well.

It should be noted as essential that the volume ratio of catalyst to polytetrafluoroethylene is more important than the weight ratio. The corresponding weight ratios from catalyst to polytetrafluoroethylene can therefore be determined from the information in the examples, by calculating from the density ratio the weight of the substances which is required to achieve the same Volume ratio as for platinum and polytetrafluoroethylene.

Claims (4)

Patent claims: 1. Fuel element with an aqueous electrolyte which adsorbs in an electrolyte carrier which is arranged between two gas-permeable, hydrophobic electrodes, characterized in that, that the electrodes contain gas-adsorbing metal particles with a surface area of 10 to 100 nr / g, those with polytetrafluoroethylene connected to a unitary mass, with 0.214 to 2.14 parts by volume of metal 1 part by volume of polytetrafluoroethylene falls. 2. Fuel element according to claim 1, characterized in that the gas-adsorbing metal consists of at least one metal from Group VIII of the Periodic Table of the Elements. 3. Fuel element according to Claims 1 and 2, characterized in that the metal is at least is a precious metal. 4. Fuel element according to Claims 1 to 3, characterized in that the gas adsorbing Metal is platinum or palladium.